1 /* $NetBSD: pread.c,v 1.8 2019/09/13 02:19:46 manu Exp $ */
2
3 /*
4 * Copyright (c) 1996
5 * Matthias Drochner. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29 /* read into destination in flat addr space */
30
31 #include <lib/libsa/stand.h>
32
33 #include "libi386.h"
34
35 #ifdef SAVE_MEMORY
36 #define BUFSIZE (1*1024)
37 #else
38 #define BUFSIZE (4*1024)
39 #endif
40
41 static char *buf;
42
43 ssize_t
pread(int fd,void * dest,size_t size)44 pread(int fd, void *dest, size_t size)
45 {
46 size_t rsize;
47
48 if (!buf)
49 buf = alloc(BUFSIZE);
50
51 rsize = size;
52 while (rsize > 0) {
53 size_t count;
54 ssize_t got;
55
56 count = (rsize < BUFSIZE ? rsize : BUFSIZE);
57
58 got = read(fd, buf, count);
59 if (got < 0)
60 return -1;
61
62 /* put to physical space */
63 vpbcopy(buf, dest, got);
64
65 dest += got;
66 rsize -= got;
67 if (got < count)
68 break; /* EOF */
69 }
70 return size - rsize;
71 }
72